Recently, a low dielectric film (low-k film) is used as an interlayer insulating film in order to decrease an inter-wiring capacitance in accordance with a demand for a high speed of semiconductor devices or the like. Since a low-k film having a lower k value is desired, a porous low-k film is used as the low-k film. This makes etching difficult during formation of BEOL (Back End Of Line) wiring.
Therefore, when the low-k film is used for the etching target film, a hard TiN film having a high etching resistance is used for a metallic hard mask as an etching mask in order to reduce damages to the low-k film during etching or ashing and improve an etching accuracy.
Currently, a PVD (Physical Vapor Deposition) method is widely used as a method for forming a TiN film for a metallic hard mask. However, a CVD (Chemical Vapor Deposition) method using TiCl4 gas as a Ti-containing gas and a nitriding gas which is widely used as a method for forming a TiN film (see, e.g., Patent Document 1), an SFD (Sequential Flow Deposition) method for alternately repeating TiN film formation using TiCl4 gas and nitriding using a nitriding gas, or an ALD (Atomic Layer Deposition) method for alternately supplying TiCl4 gas and a nitriding gas (see, e.g., Patent Document 2) is also examined as a method for forming a TiN film for a metallic hard mask.
Patent Document 1: Japanese Patent Application Publication No. H06-188205
Patent Document 2: Japanese Patent Application Publication No. 2003-077864
However, as the porosity of the low-k film is increased to further reduce the k value, a mechanical strength of the low-k film is further reduced. Even if a TiN film is used as a metallic hard mask, a groove pattern is deformed after the etching of the metallic hard mask or the low-k film.